Dodge Ram 1500 / 2500 / 3500:

air conditioning

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# 1  6/1/2011 7:20 PM

gravedigger51157
New member
Registered: 6/1/2011
Posts: 1

air conditioning

my 2001 ram 1500 a/c works fine until i brake hard or suddenly. then the cold air turns to hot air. if i turn it off, and wait a couple minutes then it works fine again, until i stop again. why is that

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# 2  6/1/2011 11:06 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1305

Re: air conditioning

Scan the computer system to see if any A/C trouble codes come up first. Repair any that might come up.

It sounds like when you make a hard stop; you are losing vacuum to the A/C system.

By applying the brakes the power brake booster uses engine vacuum. If you have a vacuum leak somewhere it will affect the vacuum to the A/C system blend door when applying the brakes.

Check all vacuum lines going into the truck. There are two check valves that if one or both malfunction will allow vacuum to escape causing the A/C blend door to move to the heat side. Running the engine will bring vacuum to the A/C system again allowing it to work properly.

VACUUM CHECK VALVE
On some engine models, a vacuum check valve is installed in the accessory vacuum supply line near the vacuum tap on the right side of the engine intake manifold.

The use of a vacuum check valve helps to maintain the system vacuum needed to retain the selected HVAC mode and vehicle speed control settings. On this engine models, it prevents the engine from bleeding down system vacuum through the intake manifold during extended heavy engine load (low engine vacuum) operation.

On other engine models, a second vacuum check valve is installed in the accessory vacuum supply line at the tee fitting near the dash panel in the engine compartment. This check valve also helps to maintain the system vacuum needed to retain the selected HVAC mode settings, but isolates the HVAC vacuum circuit from the vehicle speed control vacuum circuit. It prevents the vehicle speed control servo from bleeding down the HVAC system vacuum during extended heavy engine load operation.

The vacuum check valve cannot be repaired and, if faulty or damaged, it must be replaced.

Check out these suggestions and let me know your results. We can go on from there.


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